Polymer Microsphere Synthesis Via Droplet Microfluidic Technique And Its Application In Analytical Chemistry

Polymer microspheres refer to polymer spheres with sizes ranging from sub micrometers to hundreds of micrometers,which are widely used in fields such as petroleum industry,green energy,instrument analysis,food safety,biomedicine,and environmental engineering.There have been numerous reports on conventional techniques for the preparation of polymer microspheres at the sub-micron to micron level;However,it is difficult to synthesis uniform polymer microspheres with more than tens of microns by conventional methods,including suspension polymerization or lotion polymerization.Although the Shirasu porous glass membrane emulsification method and other techniques can meet the requirement of uniformly size,they need large costs;These factors constrain the application of polymer microspheres.To solve these problems,We conduct the preparation of uniformly sized single and double droplet in this thesis,and uses droplet as templates to synthesis solid and hollow polymer microsphere ranging from tens to hundreds of micrometers.This thesis includes three works.In Chapter 2,a microfluidic chip was designed and fabricated for the preparation of single droplets with uniformly sized oil in water（W/O）and oil in water（O/W）single droplets.By screening various surfactants and additives,the stable styrene O/W single droplets were prepared.Besides,the relationship between dispersed phase flow rate and droplet size was explored.By controlling divinylbenzene（DVB）and linear polystyrene prepolymer（LPS）concentrations,uniformly sized crosslinked polystyrene microspheres were prepared using this droplet as a template.The microspheres size can be adjusted by changing the droplet size.Compared to those conventional methods,this method has the advantages of fast synthesis time,and microspheres size can be easily controlled.In Chapter 3,homogeneous monomer solution of poly（N-isopropylacrylamide）（PNIPAM）W/O single droplets was prepared.The size of the droplet can be controlled by changing the dispersed phase flow rate.By adding gold nanoparticles（Au NPs）into the dispersed phase and polymerizing the droplets through photoinitiation,the uniform sized PNIPAM@Au NPs microsphere was prepared.We used the probe molecule 4-mercaptobenzoic acid（4-MBA）to study the effect of the temperature sensitivity of microsphere on surface-enhanced Raman scattering（SERS）detection.Based on this microsphere,we conducted SERS detection on two banned dyes with cancer risk,rhodamine B（RB）and malachite green（MG）,with detection limits of 1×10^-9 M and5×10^-9M.The above work provides a quick and simple strategy for the preparation of nanoparticle loaded hydrogels.PNIPAM@Au NPs microspheres are expected to be applied in SERS based food and environmental detection.In Chapter 4,we developed a local modification strategy based on the combination of plasma treatment technique and silane coupling reagent modification to solve the problem of difficulty in local modification of polydimethylsiloxane（PDMS）chips,achieving local hydrophilic and hydrophobic modifications inside the chip channels.By locally modifying the microchannels,it is capable to prepare oil in water in oil（O/W/O）and water in oil in water（W/O/W）double droplets.Taking PNIPAM monomer solution O/W/O double droplet preparation as an example,the relationship between three-phase flow rate and the internal/external dimensions of the double droplets was explored.PNIPAM hollow microspheres with a stable and clear cavity were prepared based on the PNIPAM monomer solution O/W/O double droplets.The above work provides a simple local modification strategy for the preparation of double droplets;Uniformly sized and stable double droplets were use as templates to prepare hollow structured microspheres.This method has advantages such as fast synthesis time and low pollution compared to conventional methods.Based on PNIPAM hollow microspheres,adsorption tests of methylene blue（MB）and RB were conducted,verifying that the microspheres have good adsorption capacity;In addition,the influence of temperature sensitive performance of PNIPAM hollow microspheres on adsorbents was investigated.The PNIPAM hollow microspheres adsorbed methylene blue were able to release adsorbents in physiological saline at 37℃,indicating the potential application as temperature sensitive controlled release carriers of drugs.